A minimally invasive procedure is a medical procedure that is performed through the skin or an anatomical opening. In contrast to an open procedure for the same purpose, a minimally invasive procedure will generally be less traumatic to the patient and result in a reduced recovery period.
However, there are numerous challenges that minimally invasive procedures present. For example, minimally invasive procedures are typically more time-consuming than their open procedure analogues due to the challenges of working within a constrained operative pathway. In addition, without direct visual feedback into the operative location, accurately selecting, sizing, placing, and/or applying minimally invasive surgical instruments and/or treatment materials/devices can be difficult.
For example, for many individuals in our aging world population, undiagnosed and/or untreatable bone strength losses have weakened these individuals' bones to a point that even normal daily activities pose a significant threat of fracture. In one common scenario, when the bones of the spine are sufficiently weakened, the compressive forces in the spine can cause fracture and/or deformation of the vertebral bodies. For sufficiently weakened bone, even normal daily activities like walking down steps or carrying groceries can cause a collapse of one or more spinal bones. A fracture of the vertebral body in this manner is typically referred to as a vertebral compression fracture. Other commonly occurring fractures resulting from weakened bones can include hip, wrist, knee and ankle fractures, to name a few.
Fractures such as vertebral compression fractures often result in episodes of pain that are chronic and intense. Aside from the pain caused by the fracture itself, the involvement of the spinal column can result in pinched and/or damaged nerves, causing paralysis, loss of function, and intense pain which radiates throughout the patient's body. Even where nerves are not affected, however, the intense pain associated with all types of fractures is debilitating, resulting in a great deal of stress, impaired mobility and other long-term consequences. For example, progressive spinal fractures can, over time, cause serious deformation of the spine (“kyphosis”), giving an individual a hunched-back appearance, and can also result in significantly reduced lung capacity and increased mortality.
Until recently, treatment options for vertebral compression fractures, as well as other serious fractures and/or losses in bone strength, were extremely limited—mainly pain management with strong oral or intravenous medications, reduced activity, bracing and/or radiation therapy, all with mediocre results. Because patients with these problems are typically older, and often suffer from various other significant health complications, many of these individuals are unable to tolerate invasive surgery. In addition, to curb further loss of bone strength, many patients are given hormones and/or vitamin/mineral supplements—again with mediocre results and often with significant side effects.
In an effort to more effectively and directly treat vertebral compression fractures, minimally invasive techniques such as vertebroplasty and, subsequently, kyphoplasty, have been developed. Vertebroplasty involves the injection of a flowable reinforcing material, usually polymethylmethacrylate (PMMA—commonly known as bone cement), into a fractured, weakened, or diseased vertebral body. Shortly after injection, the liquid filling material hardens or polymerizes, desirably supporting the vertebral body internally, alleviating pain and preventing further collapse of the injected vertebral body.
Because the liquid bone cement naturally follows the path of least resistance within bone, and because the small-diameter needles used to deliver bone cement in vertebroplasty procedure require either high delivery pressures and/or less viscous bone cements, ensuring that the bone cement remains within the already compromised vertebral body is a significant concern in vertebroplasty procedures. Kyphoplasty addresses this issue by first creating a cavity within the vertebral body (e.g., with an inflatable balloon) and then filling that cavity with bone filler material. The cavity provides a natural containment region that minimizes the risk of bone filler material escape from the vertebral body. An additional benefit of kyphoplasty is that the creation of the cavity can also restore the original height of the vertebral body, further enhancing the benefit of the procedure.
In many cases, enhancements to existing minimally invasive surgical procedures, or new applications for minimally invasive surgical procedures, necessitate the use of higher pressures to perform those procedures (e.g., the use of more viscous bone filler materials in vertebroplasty or kyphoplasty to reduce extravasation risks, or the use of smaller cement delivery needles/nozzles to enhance placement flexibility and/or reduce patient trauma). However, as higher-pressure tools are developed, it becomes more critical that overpressure conditions do not develop that could result in adverse results for patients.
Accordingly, it is desirable to provide surgical tools and techniques that limit forces and/or pressures generated by or within surgical systems.